Described examples include USB controllers and methods of interfacing a host processor with one or more USB ports with the host processor implementing an upper protocol layer and a policy engine for negotiating USB power delivery parameters, in which the USB controller includes a logic circuit implementing a lower protocol layer to provide automatic outgoing data transmission retries independent of the upper protocol layer of the host processor. The controller logic circuit further implements automatic incoming data packet validity verification and acknowledgment independent of the upper protocol layer of the host processor.